It is known that in prolonged fasted adults hepatic gluconeogenesis decreases and the utilization of glucose by brain is reduced. Little information is available regarding the rapidity of this response in * children nor the differences in the adaptive pattern between men and women. D2 glucose and D4 alanine turnover studies will be performed in children with suspected hypoglycemia after an overnight fast and again following 30 hours of fasting near the time of hypoglycemia. Sequential turnover studies will be carried out in normal adult men and women following various periods of caloric deprivation. * Children with diabetes melitus will be studied following an overnight fast utilizing stable isotopes while on subcutaneous insulin and at two different predetermined glucose concentrations while under the control of the artificial pancreas. * We plan to develop new nonradioactive technics for dynamic measurements of substrate flux in children utilizing N15, C13 and H2. At the present time we are developing methods of measuring branched chain amino acid flux utilizing N15-leucine. Recently reported studies in the perfused rat intestine has * demonstrated selective uptake and metabolism of glutamine and production of alanine, NH3, and citrulline. We presently are developing an in vitro rat intestinal preparation to define the physiologic regulation and importance of these observations. BIBLIOGRAPHIC REFERENCES: Garber, A.M., Cryer, P.E., Santiago, * J.V., Haymond, M.W., Pagliara, A.S. and Kipnis, D.M. The role of adrenergic mechanisms in the substrate and hormonal response to insulin induced hypoglycemia in man. J. Clin. Invest. 58; 7-15, 1976. Haymond, M.W., Karl, I.E., Weldon, V.V., and Pagliara, A.S. The role of growth hormone and cortisone on glucose and gluconeogenic substrates. J. Clin. Endo. Metab. 42:846-856, 1976. *